The present invention belongs to the field of aqueous nail enamel composition which contains no organic solvent, is excellent in safety for human body and long-term storage stability, and has beautiful color and gloss, and high strength and adhesion of coating film.
Conventional nail enamel compositions have the composition similar to that of organic solvent type paints. For example, they are usually composed of a resin such as a nitrocellulose and an alkyd resin, a pigment, a plasticizer and an organic solvent.
That is, the conventional nail enamel compositions are such that a pigment as a colorant is enclosed in a resin and suspended in an organic solvent, and the suspension is coated by some means and the organic solvent is volatilized to form a film. In this case, hardness of the film formed is adjusted by the remaining plasticizer. The film after use is removed by an organic solvent capable of dissolving the film.
However, since the nail enamel of the above composition contain organic solvents and plasticizers, they are used taking into consideration the restriction in use due to noxiousness to human body of the chemical substances used, the flammability of compounds in view of environmental safety, and the odor of organic solvents.
Under the circumstances, development of aqueous nail enamel compositions containing no organic solvent is demanded, and intensive effort for the development is exerted.
The present technical standard of means for making aqueous nail enamel compositions can be summarized as follows:
(1) To use water-soluble or water-dispersible resins as the constituting resins.
(2) To use organic solvents which are miscible with water as the solvents.
(3) To use hydrophilic compounds as the plasticizers.
(4) To use compounds like the above (3) as film-forming aids employed in using emulsion resins.
These efforts of development of aqueous nail enamel compositions are disclosed in Japanese Patent Nos.2686880 and 2115767 and JP-A Hei 8(1996)-225434.
However, even if the above means are employed, the conversion of the organic solvent type nail enamel compositions to aqueous nail enamel compositions still has the following technical problems to be solved.
(1) In the case of using a water-soluble resin as the resin to enclose pigment, it is difficult to design the resin to have a high refractive index because of the conditions for rendering the resin water soluble, and consequently high gloss and clear color are difficult to obtain.
(2) It is difficult to enclose separately and completely a plurality of pigments with a water-soluble resin with no bare pigment to be present.
(3) A smooth surface cannot be obtained without using a water-soluble organic solvent or a film-forming aid, and it is difficult to obtain a nail enamel composition comprising solely water.
(4) It is difficult to obtain a long-term storage stability for aqueous pigment dispersion.
(5) It is difficult to give a goodly endurable adhesive force to a nail having an oily surface using a hydrophilic resin.